The effect of the capillary forces on the desorption of hydrogels in contact with a porous cementitious material

This paper examines the desorption of hydrogels in contact with porous cementitious materials to aid in understanding the mechanisms of water release from superabsorbent polymers (SAP) into cementitious materials. The dependence of hydrogel desorption on the microstructure of cementitious materials and relative humidity was studied. It was shown that the capillary adhesion developed at the interface between the hydrogel and cementitious materials increased the desorption of the hydrogels. The size of hydrogels was shown to influence desorption, beyond the known size dependence of bulk diffusion, through debonding from the cementitious matrix, thereby decreasing the effect of the Laplace pressure on desorption. Microscopic examination highlighted a stark contrast in the desorption morphology of hydrogels with different chemical compositions.